Apparatus for handling thixotropic material



Nov. 19, 1963 E. MARSH 3,111,059

APPARATUS FOR HANDLING THIXOTROPIC MATERIAL Filed Jan. 19, 1961 2 Sheets-Sheet l X5 Z5 I 26 Nov. 19, 1963 E. MARSH APPARATUS FOR HANDLING THIXOTROPIC MATERIAL 2 Sheets-Sheet 2 Filed Jan. 19, 1961 IH I H H H INVENTOR. EAW/A/ IVA/F5 BY 44%,, MW

ATI'OF/VEYS 3,111,059 Ice Patented Nov. 19, 1963.

ical Corporation, Bristol, lla., a corporation of Dela- Ware Filed Jan. 19, 1961, Ser. No. 83,678 13 Claims. (Cl. 86-20) The present invention relates to an improved method of and apparatus for producing flow of thixotropic material. More particularly the invention relates to improvements in the method of and apparatus for treating thixotropic material described and claimed in the prior copending application of Herschel Q. Holly and myself, Serial No. 823,153, filed June 26, 1959 and entitled Apparatus For Casting Thixotropic Material.

The term thixotropic material as used in the specification and claims is intended to include those viscous materials in which the rate of flow can be increased by mechanical vibration as well as those materials which can only be made to flow by mechanical treatment. While the method and apparatus of the present invention may have other applications, it is particularly useful for easting solid fuel propellants in the casings of rocket engines.

In said prior application Serial No. 823,153, a casting can is disclosed into which the so-called solid fuel propellants, having a thick dough-like consistency, are delivered from a mixer for intermediate storage or direct use in a casting apparatus. The casting can is mounted on a vibrating table and has radial fins projecting radially from the walls of the can into the material to mechanically work the material to render it fluid. The material then flows into or from the casting can. While the casting can of the prior application operates to render the thixotropic material fluid, the material tends to flow from the center of the can at a faster rate than from the edges, and is apt to cause a blow-through when a substantial amount of the material remains in the can. Furthermore, the material is apt to trap air as it is delivered to the casting can and contain trapped air when cast in the engine casing.

One of the objects of the present invention is to provide an improved method of and casting can construction for maintaining the thixotropic material at a substantially horizontal level in the can as it is delivered therefrom.

Another object is to provide an improved method of and apparatus for treating thixotropic material to simultaneously deaerate the material and render it fluid.

Another object is to provide an improved casting can which continually propels the thixotropic material in addition to mechanically working it.

- Still another object is to provide an improved apparatus for rendering thixotropic materials fluid which is of relatively simple construction, economical to manufacture and one which is reliable in operation for performing its intended function.

These and other objects will become more apparent from the following description and drawings in which like characters denote like parts throughout the several views. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not a definition of the limits of the limits of the invention, reference being had for this purpose to the appended claims.

In the drawings:

FIGURE 1 is a view showing thixotropic material being dumped from a mixer into a casting can;

7 FIGURE 2 is a part sectional view of a casting apparatus in side elevation and showing the casting can mounted on a vibrating platform;

FIGURE 3 is an enlarged top plan view of thecasting can illustrated in FIGURE 2 with the cover removed to show the radial fin plates in the can and the depending blades projecting at an angle to the plane of the respective fin plates;

FIGURE 4 is a sectional view of the casting can in side elevation and showing the deflecting baffle overlying the outlet opening for producing a flow of the thixotropic material in a tortuous path and a gradual reductionvin the rate of flow;

FIGURE 5 is a part sectional view of the outlet from the casting can and showing a deflecting baflle of modified construction;

FIGURE 6 is a perspective view of the open top of a casting can and showing the dough-like consistency of the thixotropic material as it is delivered to a can; and

FIGURE 7 is a view similar to FIGURE 6 showing the consistency of the material resulting from vibration.

The method of the present invention is described as applied to casting so-called solid fuel propellants in rocket engines, but it will be understood that the method may have other applications to facilitate the handling of thixotropic materials. The ingredients of such solid propellants usually comprise from 70% to of solids in granular form and having consistency much like sand and other ingredients of a thick viscous consistency. The flow characteristics of the propellant material are not conventional, but instead act like certain glutenous and gelatinous preparations which exhibit the property of liquifying when subjected to internal shearing forces. Materials of this kind are known as thixotropic and it is a characteristic of such materials to set up or thicken when the shearing force ceases to act. As a result, the handling of this unusual solid propellant material and the casting of the material in rocket engines without any gaseous voids presents a considerable problem.

The material is blended in a mixer at an elevated temperature of about F., and then delivered to a deaerating vessel to remove all dissolved entrained gases including air. This has been accomplished, with at least partial success, by transferring the mixture to a casting can while the latter is vibrated as described in the prior application Ser. No. 823,153, referred to above. The vibration of the casting can produces internal shearing forces in the material which renders it fluid, retains the homogeneity of the ingredients of the mixture and tends to release the trapped gases. When the material is to be cast the casting can is again vibrated to cause the material to flow from the casting can through an outlet opening in the bottom thereof which also tends to prevent the reintroduction of any gases into the material. In order to increase the flow rate of the sticky mass of material from the casting can, its temperature is maintained elevated and a pressure fluid is supplied to the top surface of the material in the can.

However, a plug type flow of the thixotropic material results with a liquifica tion in the walls of the outlet conduit and an en masse movement of the material without any velocity gradient into the central portion of the moving mass. This characteristic movement of the material also extends upwardly into the casting can so that a central cavity is formed in the material over the outlet which is sometimes roughly cylindrical and sometimes in the shape of a vortex. In either case, after a portion of the propellant has been delivered from the center of the casting can the central cavity reaches to the outlet opening at the bottom of the can. The pressure fluid, such as compressed air, then flows through the outlet opening while a portion of the material still :13 remains in the can. This undesirable occurrence is known as a blow-through and in addition to limiting the amount of material delivered from a can also causes the material cast in the engine casing to be infused with the pressure fluid.

In accordance with the method of the present invention, the material is first vibrated to render it fluid and then its direction and rate of flow are changed as it moves toward the outlet opening to maintain a substantially horizontal level in the casting can as it is delivered therefrom. In addition to vibrating the material to render it fluid, the material is propelled in a horizontal plane to further maintain a horizontal level of the material in the casting can. As the material is vibrated and propelled, it is caused to flow radially outward and then radially inward over a baffie disc overlying the outlet opening to change its direction of flow. It has been found desirable to gradually decrease the rate of flow in addition to changing the direction of flow and this is accomplished by restricting the opening between the baffle and bottom of the container. Preferably, the area of the opening between the baffle and bottom of the container and area of the outlet opening have a ratio of 1.25 to 1.00.

Fluid pressure is applied to the top of the mass of the material in the casting can to augment the rate of flow. However, in accordance with the present invention the top of the mass of material in the casting can is alternately subjected to a gauge pressure substantially above atmospheric of, for example, 40 pounds per square inch and a vacuum of, for example, 2 8 inches of mercury below gauge. This alternate pressure and vacuum further tends to work the material and cause gas bubbles to move upwardly through the material into the air space. The material also is heated in the casting can to maintain it at a temperature best suited for the flow of material from the can.

The material flowing through the outlet from the bottom of the casting can is then directed through a delivery tube to a rocket engine where the material is cast. Additional vibrating means may be provided around the outlet tube to insure flow of the material therethrough. It has been found that the propellant material may be cast in accordance with the method of the present invention at rates of 80 to 160 pounds per minute with negligible quantities of gas trapped in the cast propellant.

A preferred form of apparatus for performing the method of the present invention is illustrated in the accompanying drawings. Referring to FIGURE 1 of the drawings, a batch of the thixotropic mate-rial, such as a liquid polymer used as a rocket propellant, is processed in a mixer 19 which may be tilted to dump the dough-like mass of material into the open top of a casting can 11. The material falls into the can 11 in separate masses or chunks as illustrated in FIGURE 6. Preferably, the casting can 11 is mechanically vibrated while the material is being delivered to the can from the mixer 10 to cause the material to flow in the can to form a continuous mass without voids as illustrated in FIGURE 7. To this end, the casting can 11 may be mounted on the vibrating table 12 of the casting apparatus 13 during a filling operation, or may be mounted on a similar but separate vibrating apparatus during such filling. Thus, the thixotropic material may be delivered from the mixer .10 to casting can 11 and from the casting can to a rocket engine casing 14 while mounted on the casting apparatus 13, or alternately, the material may be placed in a can at the mixer for temporary storage or for transfer to a casting apparatus located remotely from the mixer 10/.

The casting apparatus 13 is like that illustrated and described in the prior application Serial No. 823,153, referred to above. The platform 12 is mounted on a series of angularly arranged coil springs 15 acting between the base 16 and the platform and the platform and the springs have a natural frequency of vibration at a particular load. The platform 12 is vibrated by a drive shaft 17 having eccentrics 18 connected to the platform 12 through connecting rods 19. The casting can 11 is mounted on legs 20 which are clamped to the platform 12 so that the casting can vibrates with and at the same frequency as the table 12 in a particular installation. When a casting can 11 of twenty gallons capacity is used, the total load to be vibrated is 1092 pounds of which 810 pounds is the casting can filled with propellant. Springs 18 may be designed so as to produce a natural frequency of 385 cycles per minute for this particular load. Thus, the shaft 17 is initially rotated at 385 r.p.m. and the speed may be gradually increased as the load decreases to maintain the vibration at the natural frequency of the spring load. The vibration of the platform 12 is transmitted through the legs 20 to the casting can 11.

The casting can 11, see FIGURES 2 to 4, has a jacket 25 surrounding its outer wall to provide an annular space 26 for circulating a heating medium to maintain the material at a desired temperature of, for example, F. The legs 20 are attached to the depending skirt 27 formed by the wall of jacket 25. The open top of the can 11 is closed by a removable cover 28 which is held on the can by a ring clamp 29 and safety clamps 29a. Fin plates 30, four being shown, extend radially inward from the peripheral wall of the can ll and terminate adjacent the axis of the can. An outlet opening 32 is located centrally in the bottom wall of the casting can 11 through which the material therein may be discharged. As thus far described, the casting can 11 is substantially identical with the casting can illustrated in the prior application Serial No. 823,153, referred to above.

In accordance with the present invention, each of the fin plates 30 has spaced depending blades 31 extending at an acute angle to the plane of the fins. The depending blades 31 may be formed by slitting the lower portion of a fin plate 30 and twisting the depending portions of the plate between the slits so that the upper portion of the plate constitutes a fin 30 and the depending twisted portions constitute the depending blades 31. In the illustrated embodiment, however, the fins 30 and depending blades 31 are formed as separate elements having slots to adapt the parts to be interleaved nad welded to each other. With this construction the vibration of the platform 12, see FIGURE 2, is transmitted to the walls of the can 11 and from the walls through the inwardly directed radial fins 30 and depending blades 31. As the fin plates 30 and depending blades 31 project into the material they mechanically work the material and set up internal shear forces to render the material fluid. In addition, the angular depending blades 31 act as paddles to propel the material in a horizontal plane about the outlet opening 32. In the illustrated embodiment the fin plates 30 are shown extending radially, but it will be understood that they may extend at an angle to a radial plane and the blades 31 may have other angular relations to the fin plates 30.

Each fin plate 30 may be fixedly attached to the side walls of the casting can 11 as in the prior application Serial No. 823,153, referred to above. However, in accordance with an improved construction illustrated herein, the fin plates 30 and depending blades 31 are removably mounted in the casting can 11 to facilitate removal as a unit and provide free access to the interior of the can and fin plates and blades for better and faster cleaning, repair or replacement. To this end, the outer ends of the fin plates 30 are fixedly attached to the inner periphery of a cylindrical sleeve 64, see FIGURE 4, of smaller diameter than the internal diameter of the casting can 11 and adapted to slide into and out of the can. The upper edge of the casting can 11 has an annular rim 65 and the sleeve 64 has a cooperating peripheral rim 66 adapted to overlie the rim 65 on the can. A gasket 73 located between the rims 65 and 66 is composed of a compressible material to adapt the rims to be clamped in sealing engagement and the rims have a cooperating rib and groove 67. Thus, the engagement of rim 66 on sleeve 64 with the rim 65 on the can 11 supports the fin plate unit on and properly positions the unit in the casting can 11. Rims 65 and 66 are connected by a removable ring clamp 68 overlying adjacent radially projecting ribs 69 and 70 on the rims. A similar ring clamp 29 is provided between a rib 71 on the rim 66 and a rib 72 on the cover 28. Thus, the assembly of fin plates 30 and sleeve 64 may be mounted on or removed from the casting can 11 as a unit so that the depending blades 31 extend to a position adjacent the bottom of the can.

In addition, a baffle plate 35 is mounted in the casting can 11 in spaced relation to the outlet opening 32 to change the direction of flow of the material as it flows from the can. In the embodiment of the invention illustrated in FIGURE 4, the deflecting baflie 35 is in the form of a disc coaxial with the outlet opening 32 and projecting radially beyond the periphery of the opening. The disc 35 is mounted on a spider-like frame 36 having spaced upright stanchions 37 around the outlet opening 32. A conical nose 38 depends from the spider-like frame 36 and overlies the outlet opening 32 at its axis. The defleeting baflle 35 is attached to the frame 36 by a bolt 39 and the foot of the frame 36 is attached to the bottom wall 33 of the can by bolts 40. Bolts 40 also attach a radial flange of an outlet fitting 41 to the bottom wall 33. Gaskets 42 and 43 are positioned between the bottom wall 33 and the foot of the frame 36 and flange of outlet fitting 41, respectively, to seal the joints therebetween.

The area between the spaced uprights 37 of the frame 36 provides openings through which the material flows and the ratio of this area to the area of the outlet opening 32 preferably has a ratio of 1.25 to 1.00. An inverted cup 44 is provided between the top of the frame 36 and the baffle 35 to control the area between the uprights 37 of the spider frame 36. Separate cups 44 having flanges of dilferent depths may be used to provide diiferent material flow ratios. A flexible tube 45, see FIGURE 2, connects the outlet fitting41 from the bottom of can 11 to a nozzle 46 for delivering the material to a rocket engine casing 14. A valve 47 for squeezing the flexible conduit 45 adjacent the fitting 41 controls the flow of material from the casting can 11 to the engine casing 14. Additional vibrating devices 48 are provided around the flexible tube 45 to insure flow therethrough.

Cover. 28 has an inlet connection 50 to which fluid under pressure is delivered from a source indicated as a pump 51. The inlet connection 50 includes a valve 52 for controlling flow of the pressure fluid thereto. A second vacuum connection 53 is provided on cover 28 connected to an exhauster indicated as an exhaust pump 54. Connection 53 has a valve 55 for controlling the flow. Valves 52 and 55 are connected by a connecting rod 56 to simultaneously open one valve and close the other as the rod is reciprocated in opposite directions. One form of casting can construction having now been described in detail, the mode of operation is next explained.

When the thixotropic propellant material is to be cast in a rocket engine casing 14, a casting can 11 filled with the thixotropic material is mounted on the platform 12 of the natural frequency vibrating apparatus 13 and operation of drive shaft 17 is initiated to vibrate the can and material therein. The vibration is transmitted through the fin plates 30 and depending blades 31 to work the material and set up internal shear forces therein which render the material fluid. In addition, the depending angularly arranged blades 31 propel the fluid material in a horizontal plane. When the material has been rendered fluid, the outlet valve 47 and the pressure control valve 52 are opened. The material then flows downwardly under pressure but is deflected laterally by the baifle plate 35, see FIGURE 4, to flow in under the baflle to the outlet opening 32. The material flows through the outlet opening 32 and tube 45 into the rocket engine casing 14 where it is cast around the core. The additional vibrators 48 on the outlet conduit 45 are also actuated to maintain the flow of the thixotropic material therethrough. Thus, the material flowing to the outlet opening 32 from casting can 11 changes its direction from vertical to horizontal outwardly, then from outward to inward horizontally and again vertically. Simultaneous with the change in direction of the material, the path of flow is restricted. As a result of these actions the level of the material in the casting can 11 is maintained substantially horizontal as it flows therefrom so that no blow-through will occur until substantially all of the material in the can has been delivered therefrom.

To augment the flow of the thixotropic material, a heating medium is supplied to the space 26 between the jacket 25 and side Wall of the casting can 11 and a pressure fluid is supplied from pump 51 through inlet conduit 50 and valve 52 onto the top of the materialand a vacuum is drawn from the top of the material through the valve 55, conduit 5-3 and vacuum pump 55 in alternate cycles by moving the valve actuator 56 in opposite directions. The pressure fluid acting on the top of the material augments its flow while maintaining a substantially horizontal level in the can 11; and the vibration together with the vacuum causes gaseous bubbles to flow upwardly through the material. As a result of the improved construction in the casting can 11, a better casting is produced having fewer gaseous voids and at a faster rate than has heretofore been possible without danger of blow-through before all of the material has been discharged from the can.

FIGURE 5 illustrates a modified construction of a bafile or deflecting plate 60 having an upwardly directed conical nose 61 at the axis and a flaring conical skirt 62 at the periphery of the nose. The baflle 60 is mounted on the bottom 33' of the casting can 11' by means of shouldered bolts 63 which hold the baffle in spaced relation to the outlet fitting 41. In the modified construction, the shouldered bolts 63 take the place of the inverted cup 44 for controlling the spacing of the baffle from the bottom wall. The form of construction illustrated in FIGURE 5 operates in the same way as described with respect to the form of the invention illustrated in FIGURE 4.

It will now be observed that the present invention provides an improved method of and casting can construction for maintaining thixotropic material at a substantially horizontal level in a can as it is delivered therefrom. It will also be observed that the present invention provides an improved method of and apparatus for treating thixotropic material to simultaneously deaerate the material and cause it to flow. It will further be observed that the present invention provides an improved casting can which propels the thixotropic material in addition to working it and causing it to flow in a path continuously changing in direction and progressively decreasing the flow rate. It will still further be observed that the present invention provides an apparatus for rendering thixotropic material fluid which is of relatively simple construction, economical to manufacture and one which is reliable in operation for performing its intended function.

While two forms of construction of a casting can are illustrated and described, it will be understood that further changes may be made in the construction and arrangement of elements without departing from the spirit or scope of the invention. Therefore, without limitation in tln's respect, the invention is defined by the following claims.

I claim:

1. Apparatus for producing flow of a highly viscous material from a container having an outlet opening comprising a vibrating platfonm, means for mounting the container on the platform for vibration therewith, fin plates mounted on the container for vibration therewith and extending into the material to transmit vibration from the platform to mechanically work the material, and a deflection plate overlying the outlet opening in spaced relation to the wall of the container adjacent the outlet whereby to produce a change in the direction of flow and a gradual reduction in flow rate of the material to maintain the material at a substantially horizontal level in the container as it flows therefrom.

2. Apparatus for producing flow of a highly viscous material from a container having a centrally located outlet opening in the bottom wall thereof comprising a vibrating platform, means for mounting the container on the platform, fin plates mounted on the container and projecting inwardly from the sides of the container into the material, at least a part of each fin extending at an angle to the plane of the remainder of the fin whereby the fin plates transmit the vibration from the platform to work the material and propel it in a direction at right angles to its direction of flow through the outlet opening.

3. Apparatus for producing flow of a highly viscous material from a container having a centrally located outlet opening in the bottom wall thereof comprising a vibrating platform, means for mounting the container on the platform for vibration therewith, fin plates projecting inwardly from the sides of the container into the material, a deflection plate overlying the outlet opening in spaced relation to the bottom Wall of the vessel, and at least a part of each fin extending at an angle to a radial plane through the axis of the outlet opening to transmit the vibration from the platform to mechanically Work and propel the material, whereby to produce a reduction in the flow rate and change in the direction of flow to maintain the material at a substantially horizontal level in the container as it flows therefrom.

4. Apparatus in accordance with claim 1 in which the material is a thixotropic rocket propellant fuel, the container is a can containing a supply of material for casting, a rocket engine casing, and a conduit extending from the outlet opening in the casting can to the engine casing to cause the propellant fuel to flow from the container to the casing.

5. Apparatus in accordance with claim 1 in which the container is of generally cylindrical shape, the outlet opening is circular and located in the bottom wall of the container axially thereof and the deflection plate comprises a disc spaced vertically from the bottom wall of the container and having a peripheral edge spaced radially from the peripheral edge of the outlet opening to provide an annular passageway extending radially inward to the outlet opening from the container.

6. Apparatus in accordance with claim 5 in which the deflection plate has a curved upper surface and a conical under surface overlying the outlet opening in the container, and the areas of the passage-way between the outer edge of the plate and bottom Wall and the outlet opening from the container having a ratio of 1.25 to 1.00.

7. Apparatus in accordance with claim 6 in which an inverted cup-shaped member is provided between the deflection plate and bottom wall of the container to de- 8 fine the area of the passageway in the path of flow of the material.

8. Apparatus in accordance with claim 2 in which the part of each fin extending at an angle to the remainder of the fin comprises a plurality of spaced blades depending from the fin element.

9. Apparatus in accordance with claim 8 in which the fin plates extend radially inward from the side wall of the container and have vertical slots therein, the depending blades having vertical slots at one end, and the blades being interleaved with the fin plates at the slots and attached to each other to form a one-piece construction.

10. Apparatus in accordance with claim 1 in which the fin plates are constructed in a self contained unit removably mounted on the container comprising a cylindrical sleeve, said fin plates attached to and projecting inwardly from said sleeve, and radially projecting rims on said container and sleeve.

11. A container for thixotropic material which may be bodily vibrated to render the material therein fluid for flow into or from the container, said container having enclosing walls including a side wall concentric about a longitudinal axis and a bottom wall transverse to the axis having an outlet opening at the axis, fin plates attached to the side wall and extending inwardly from the wall, and a deflecting baflle plate having a circular periphery concentric with the axis and of a substantially greater diameter than the outlet opening to overlie the outlet opening in close spaced relation thereto to provide an annular restrictive passageway therebetween.

12. A cylindrical container for thixotropic material which may be bodily vibrated around a longitudinal axis to render the material therein fluid for flow into or from the container, said container having enclosing walls comprising a side wall and a bottom wall having an outlet opening at the axis, fin plates attached to said side wall and extending inwardly from the wall, a deflecting baffle plate having a circular periphery concentric with the axis and of a substantially greater diameter than the outlet opening to provide an annular restrictive passageway therebetween, and at least a part of each fin plate extending at an angle to the remainder of the fin.

13. A container for thixotropic material in accordance with claim 12 in which the fin plates each comprise a section extending radially inward from a wall of the container, and a plurality of spaced depending blades extending at an angle to the first section.

References Cited in the file of this patent UNITED STATES PATENTS 166,579 Atwood Aug. 10, 1875 953,078 Whitcomb et a1 Mar. 29, 1910 988,798 Maxim Apr. 4, 1911 2,426,619 Knight Sept. 2, 1947 2,736,461 Dueringer et al. Feb. 28, 1956 2,900,109 Hoopes et al. Aug. 18, 1959 

1. APPARATUS FOR PRODUCING FLOW OF A HIGHLY VISCOUS MATERIAL FROM A CONTAINER HAVING AN OUTLET OPENING COMPRISING A VIBRATING PLATFORM, MEANS FOR MOUNTING THE CONTAINER ON THE PLATFORM FOR VIBRATION THEREWITH, FIN PLATES MOUNTED ON THE CONTAINER FOR VIBRATION THEREWITH AND EXTENDING INTO THE MATERIAL TO TRANSMIT VIBRATION FROM 